Three-phase current source rectifier (CSR) (also sometimes referred to as a “buck-type rectifier”) may feature a step-down function, smaller filter size, inrush current limiting capability, and the potential to achieve high efficiency. It may be applied as the active front-end in high-efficiency power supplies for telecommunication and data center, where 480 V or 380 V ac voltage was stepped down to 400 V dc voltage in a single conversion stage. It may be used as the off-board dc fast charger for electric vehicles to increase the efficiency. In high power applications such as DC arc furnace and induction melting, CSRs may largely reduce the size, loss and cost of the transformer and harmonic filter. For variable speed motor drive application, it may reduce the input filter size and increase the power density.
The switches in CSRs may be Reverse Blocking Insulated-Gate Bipolar Transistor (RB-IGBT) with reverse-blocking capability to operate under AC voltage. The RB-IGBT was developed to reduce the conduction loss for current source converters and matrix converters. But the switching loss of RB-IGBT may be much higher compared with standard IGBTs, due to its longer “tail current”, worse voltage overshoot and larger reverse recovery current. A symmetric gate-commutated thyristor (GCT) may have a blocking voltage of several kVs and may be used in high-voltage application with less than 1 kHz switching frequency. In most applications of pulse width modulated (PWM) CSRs, the switches may be formed by connecting an active device (IGBT, MOSFET or JFET) with a diode in series. Even with several devices in parallel in one switch, the high conduction/current loss may still account up to 50% of the total converter loss in traditional CSRs.
Therefore, there is a need for an improved CSR with lower conduction loss without significantly increasing the size of devices in the CSR.